Abrasive wheel



July 25, 1950 Filed Feb. 19, 1949 A; M. FROST ABRASIVE WHEEL 2Sheets-Sheet 1 INVENTOR.

141 5 TIN M. FROST July 25, 1950 A. M. FROST 2,516,693

ABRASIVE WHEEL Filed Feb. 19, 1949 2 Sheets-Sheet 2 INVENTOR. HusT/N M.FROST Patented July 25, 1950 ABRASWE lEL Austin M. Frost, Nunrla, N. lL,assignor to The Carborundnm Company, Niagara Falls, N. in... acorporation of Delaware Application February 19, 1949, Serial No. 77,383

3 Claims.

qcore or body of such wheel.

Other objects of the present invention are to provide means wherebyabrasive segments are held to the body or core of a segmental abrasivewheel by fastening means which are under tension and which thus tend topull the segments and the body or core together, and to provide suchabrasive wheels which are light in weight, easily assembled andinexpensive to manufacture.

Still further objects of the invention will be perceived from thefollowing description.

In segmental abrasive wheels of the type used in manufacturing groundwood pulp, a type of construction has become common which involves theuse of abrasive segments assembled into a cylinder within which concreteis poured to form a core or center. Various means have been provided forholding the segments to the concrete cores. Such means have usuallyconsisted of metal bolts 01' studs embeddedor held in the segments andin the cores. Most of such means have been unsatisfactory since, as theabrasive wheels are operated at elevated temperatures, there are imposedupon such fastening means, stresses resulting from variations anddifferences in thermal expansion, as well a the centrifugal forcetending to pull the segments away from the cores when the wheels arerotating. There is also transmitted to the fastening means themechanical shock and stress occasioned by the grinding of the logs. Allof these forces have tended toward loosening the abrasive segments andsuch loosening, once begun, speedily results in failure of the wheels bythe loss of one or more segments.

According to the present invention, fastening mean are provided whichsecurely hold the abrasive segments to the concrete core or center ofthe abrasive wheel. This is accomplished by causing the abrasivesegments to be held under a definite tension tending to draw them to afirm seat against the core. or support in contrast to merely providingresistance to displacement of the segments in a radial direction.Consequently the life ofthe wheel is greatly prolonged as theprogressive deterioration which follows from the slight loosening of thesegments as a result of differences in thermal expansion, etc. isavoided.

In the accompanying drawings,

Ill

Fig. l is an elevational view, partly in section, of a segmentalabrasive wheel according to the present invention; and

Fig. 2 is a fragmentary enlarged side view of a portion of the segmentsand core, with portions broken away to provide a better view of thefastening means.

Referring to the drawings in detail, it is a composite segmentalabrasive wheel according to the present invention. The surface of wheelit is an annulus composed of a plurality of abrasive segments l I whichare mounted on a concrete core or center l2 and held thereto byfastening means designated generally by the numeral l3. Embedded withinconcrete core 12 are reinforcing rings l4 and hubs l5.

Abrasive segments I l are formed from granular abrasive material andbonding material in a manner well known in the art. These segments havea curved outer surface is, parallel edges ill and end surfaces it normalto the curvature of face it. In each end of segments ll there are formedpockets 89 extending from the end surfaces toward the center of thesegments and communicating by slots 20 with the recesses 2i formed atthe base of each end of the segments. The floor 22 of each pocket l9 andthe surface 22 forming the top side of each recess 2i are preferablyparallel and in planes normal to the planes of the segment ends l8.

Pockets it, slots 20 and recesses 28 are designed for the accommodationof fastening means 93. Each of such means comprises an elongated bolt 23having a head 24 and, screw-threadedly attached to its free end, a nut25. Loosely fitting on bolt-23 is a sleeve 26 which is retained betweenwashers 2i and 28 which are mounted on bolt 23 on each side of saidsleeve.

Bolts 23, nuts 25 and sleeves 26 may be conveniently formed of a lowcarbon steel as may also washers 2'5 which, in the accompanying claims,are called permanent washers. Washers 2b, which in the claims aredescribed as destructible washers, comprise a material that is initiallystrong in the condtion in which it is placed in use but which, underproper predetermined conditions. will be deformed or disintegrate, thuslosing its efiectiveness as a washer. It is preferred to form washer 28in three sections with outer layers 29 of steel or other suitable metaland interior layer 3i! of a less resistant material. Layer 3t may beformed, by way of example, of thermoplastic materials such as cellulosenitrate and cellulose acetate which at room temperatures as have highcompressive strength, but at moderately elevated temperatures soften andnow under pressure. materials such as casein which soften by the actionof water, or low melting metals such as tin or alloys thereof. Underfavorable circumstances one or both of the metal layers 20 may bedispensed with. -The purpose of these layers is to distribute over thedestructible portion of the washer 28 loads which are applied theretothrough sleeve 26 and prevent mechanical damage to the destructiblelayer 30. where such protection is unnecessary, layers 29 may beomitted.

In assembling an abrasive wheel according to the present invention, boltheads 24 are inserted in each of the pockets or cavities IQ of theabrasive segments II. It is in some cases desirable to provide a smooth,even seat for bolt heads 24 by casting a suitable bearing metal, shownas 24', around said heads in pockets i9. Destructible washers 28 aremounted on the bolts against the walls 22 of recesses 2i and held inthat position by sleeves 26 which are retained on bolts 23 by permanentwashers 21 and nuts 25. Tightening of nuts 25 while the bolts are inthis positionwill result in the clamping of the abrasive surroundingslots 20 between the bolt heads 2 and washers 28. Although, as statedabove, it n preferred to assemble the fastening means with the segmentsin such manner that bolt heads 24 are contained in pockets it, it willbe understood that, in assembling the fastening means with segments,bolts 23 may be reversed so that nuts 2! are so contained and heads 25extend outwardly from the segments i i.

Nuts 25 are preferably tightened until the shanks of bolts 23 are eachunder a definite, predetermined tensile stress. The tensile stressapplied should be sufllcient to insure that the segments will be firmlyseated upon the concrete core when destructible washers 28 have hadtheir effectiveness removed. It is preferred to have 'this stress of theorder of 890 1 p. s. i. 9.1-.

though higher tension may be employed within the strength limitations ofthe steel used for bolts 23. It will be realized that sleeves 25 are, ofcourse, at the same time put under compressive stresses equal to thetension in bolts 23 as are also the portions of abrasive segments llsurroundin slots 20.

After the necessary number of abrasive segments H required to form anabrasive wheel of the desired size have been thus equipped with bolts,sleeves, washers and nuts, the abrasive se ments are assembled in theform of an annulus or cylinder. Such assembly may be convenientlycarried out by the use of a fixture within which the segments are placedwith the free ends of bolts 23 extending inwardly toward the center ofthe fixture.

The joints betw :en the abrasive segments are, as shown by the drawing,filled with material 3|. Such filling material serves to cushion thesegments H and restrain them against sideways movement. It should besufiiciently resilient to permit expansion of the segments under theinfiuence of heat and to maintain the joints filled when the segmentshave contracted. It should also be resistant to the action of water toprevent its deterioration and disintegration, which would leave theedges of the segments unsupported and permit spalling and crackingthereof.

A number of materials have been disclosed in the prior art which may beused in providing this resilient joint filler. The type of material usedis a matter of choice. If desired or found neces- '4 sary the sides andends of the segments may be coated with adhesive to hold the jointfilling material in place. The filling material is preferably insertedbetween the segments as the annulus of abrasive segments is built up inthe fixture mentioned above. It is also preferred to coat the bottoms ofthe abrasive segments with a waterproofing material to minimize theabsorption of water from the wet concrete which is poured inside theannulus of segments and thus avoid impairing the quality-of the concreteadjacent thereto.

A cylindrical form (not shown) is inserted within the fixture and-insidethe annulus of segments to provide for the insertion of a shaft andconcrete may then be poured between the form and the abrasive segmentsso asto embed the shanks of bolts 23, the sleeves 26, nuts 25 andwashers 21 and 28. Prior to or during the pouring of the concrete,reinforcing rings I4 and hubs it are preferably inserted in the fixturebetween the cylindrical form and theabrasive segments to serve asstrengthening means for the 'concrete core or center and as guides forcentering the wheel on a shaft. After theconcrete core or center has setthe completed wheel may be removed from the fixture.

At this stage the segments are mechanically held to the concrete core bythe interlocking of the core with the washerszl on bolts 22. Bolts 23are under tension but this force is not transmitted to the concretesince the nuts 25 by which bolts 23 are tensioned are reacting againstsegments ii through sleeves 26 and washers 21 and 28. Certain pulpwheels of the prior art have relied upon holding means similar to thisto maintain the abrasive segments in position as the tension in thebolts will make it diflicult to pull the abrasive segments away from thecore. During the setting and drying of a concrete core, however, thereis often some tendency toward shrinkage and it may then happen,therefore, that the abrasive segments are not held firmly to theconcrete core. Thus, while they may be resistant to outward movement, itis possible, because of their failure to fit tightly against the core,ot impart some sidewise movement to the segments which will, ifcontinued, cause movement of the bolts and eventually result in failureof the segment structure or the holding means.

By the improvement of the present invention these dif'ficulties areovercome since washers 28, being destructible, may-be suitably actedupon so as to remove them as an effective operative part of the holdingmeans, thus releasing sleeves 26 from compression and permitting thetension in bolts 22 to positively draw the abrasive segments I i,through the action of the bolt heads 2! against the bottoms of pocketsl9, to a firm and positive seat against the core. The concrete of thecore between washers 21 and abrasive segments I I will then be undercompression as will also be the abrasive surrounding slots 20.

The destruction or failure of washers 28 need not take place at anyspecified time. If, for example, a cellulose nitrate composition, suchas Celluloid, is used in forming destructible layer 20 they may well bemaintained effective as washers until the abrasive wheel is placed inuse, if in such use the temperature of the wheel is raised to the pointwhere the Celluloid layers will flow.

the hot water which will penetrate through the wheel to the washers willcause softening of the casein and consequent loss of compressivestrength. Of course, where suitable washers 28 are used heat treatmentof the abrasive wheel can be employed if desired to relieve thecompression in fastening means 13 by causing destruction ordisintegration of layers 30 prior to placing such abrasive wheels inuse.

It will be noted that the construction of segmental abrasive wheelsaccording to the present invention is simple. No expensive alloys arenecessary for the bolts by which the segments are held to the core orthe other fittings and it is easy to assemble the segments carrying thebolt assemblies into a cylinder for pouring the concrete core or center.

In the drawings the abrasive segments have all been shown the same sizeand arranged in an even pattern. It will be realized, of course, thatthis is not necessary but that by having certain of the segments largerthan others a pattern of segments can be obtained in which the joints ofthe segments are not in line. This is desirable in some cases and sucharrangements are disclosed in various patents of the prior art. It willalso be realized that numerous other modifications and changes may bemade in the construction described in this specification and shown inthe drawings without departing from the spirit of the present invention.It is therefore desired that the invention shall not be con-,

- sidered limited except by the scope of the app nded claims.

I claim:

1. A segmental abrasive wheel having an annular rim comprised of aplurality of abrasive segments, each of such segments being adapted tobe engaged by fastening means, a concrete core supporting said abrasiverim and providing means for mounting said abrasive wheel upon a shaft,and a plurality of fastening means comprising bolts, each includingahead and a nut at opposite ends thereof and a sleeve surrounding saidbolt, one end of each of said bolts being engaged with one of saidabrasive segments, the other end thereof and said sleeve being encasedin said concrete core, each of said bolts being under tension and havinga destructible washer mounted thereon at the end of said sleeve adjacentto said abrasive segment, said destructible washer being held undercompression between-its associated sleeve and a portion of said segmentby pressure exerted thereon through said sleeve by the tension of itsassociated bolt.

2. A segmental abrasive wheel having an annular rim comprised of aplurality of abrasive segments, each of such segments having a pluralityof recesses each adapted to receive fastening means, a concrete coresupporting said abrasive rim and providing means for mounting said wheelupon a shaft, and a plurality of fastening means comprising bolts, eachincluding a head and a nut at opposite ends thereof and a sleevesurrounding said bolt, one end of each of said bolts being engaged inone of the recesses in said abrasive segments, a permanent washermounted on each of said bolts between the other end thereof and saidsleeve, and being encased with said other end and said sleeve in saidconcrete core, each of said bolts being under tension and having adestructible washer mounted thereon at the end of said sleeve oppositefrom said permanent washer, said destructible washer being held undercompression between its associated sleeve and a portion of one of saidsegments by pressure exerted thereon through said sleeve by the tensionof its associated bolt.

3. A segmental abrasive wheel having an annular rim comprised of aplurality of bonded abrasive segments, each of such segments having aplurality of recesses each adapted to receive fastening means, aconcrete core supporting said abrasive rim and providing means formounting said wheel upon a shaft, reinforcing means embedded in saidconcrete core and a plurality of fastening means comprising bolts, eachincluding a head and a nut at opposite ends thereof and a sleevesurrounding said bolt, one end of each of said bolts being engaged inone of the recesses in said abrasive segments, a permanent washermounted on each of said bolts between the other end thereof and saidsleeve and being encased with said other end and said sleeve in saidconcrete core, each of said bolts being under tension throughout itslength between said head and said nut and having a destructible washermounted thereon at the end of said sleeve opposite from said permanentwasher, said destructible washer being held under compression betweenits associated'sleev and a portion of one of said segments by pressureexerted thereon through said sleeve by the tension of its associatedbolt.

AUSTIN M. FROST.

REFERENCES 'CITED The following references are of record in the file ofthis patent:

UNITED STATES PATEN'I'S 2,447,943 Jeppson Aug. 24, 1948

